Various products have been provided in the past for this type of treatment. In particular, EP 542,598, the contents of which are incorporated here by way of reference, provided salified or quaternized, fluorinated acrylic copolymers comprising, by weight:
(a) 50 to 92%, preferably 70 to 90%, of one or more polyfluorinated monomers of general formula: ##STR1## in which Rf represents a straight- or branched-chain perfluorinated radical containing 2 to 20 carbon atoms, preferably 4 to 16 carbon atoms, B represents a bivalent chain sequence which is bonded to O via a carbon atom and which can contain one or more oxygen, sulphur and/or nitrogen atoms, one of the R symbols represents a hydrogen atom and the other a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms;
(b) 1 to 25%, preferably 8 to 18%, of one or more monomers of general formula: ##STR2## in which B' represents a linear or branched alkylene radical containing 1 to 4 carbon atoms, R' represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, the R.sup.1 and R.sup.2 symbols, which are identical or different, each represent a hydrogen atom, a linear or branched alkyl radical containing 1 to 18 carbon atoms or a hydroxyethyl or benzyl radical, or R.sup.1 and R.sup.2, together with the nitrogen atom to which they are bonded, form a morpholino, piperidino or 1-pyrrolidinyl radical;
(c) 1 to 25%, preferably 2 to 10%, of a vinyl derivative of general formula: EQU R"--CH.dbd.CH.sub.2 (III)
in which R" can be an alkyl carboxylate or alkyl ether group containing from 1 to 18 carbon atoms;
(d) 0 to 10%, preferably 0 to 8%, of any monomer other than the monomers of formulae I, II and III.
These fluorinated copolyers, which are completely dilutable with water, can be applied on various substrates, such as leather, nonwovens, construction materials, paper and cardboard. In particular, they can be applied on paper according to various techniques (in a size press or in the body of the material), thus conferring excellent hydrophobic and oleophobic properties on the paper, without requiring adjuvants (sequestering agents, retention agents, fixing resins, and the like).
Such types of paper are used in the field of the packaging of wet and/or greasy foodstuffs in markets as varied as the biscuit/Viennese bread and buns sector, the fast-food industry, the margarine and butter market, the meat and poultry market, the field of chocolate or coffee, deep-frozen products or the market for dry food for dogs and cats (pet food).
In the case of animal food, the fluorinated treatment must be capable of providing a barrier to particularly aggressive fats (fatty acid esters), in order to prevent the appearance of stains related to the migration of these fats, in particular into the corners and the folds of the packagings.
In order to obtain an improvement in the barrier effect to fats, it is advantageous to combine the fluorinated acrylic copolymers described in Patent EP 542,598 with a starch or with a polyvinyl alcohol. However, in the case of certain types of paper, the barrier to fats is only obtained after a fairly long maturing time for the paper, by simple storage at room temperature for two to three weeks. The need to have to store the paper before using it to produce packagings, the impossibility of controlling the quality of his production at the outlet of the machine and the need to manage the delivery times to his customers present the paper manufacturer with significant problems.